Surgical needles and methods of manufacturing surgical needles are well known in the art. Surgical needles typically consist of a shaft-like member, which may be curved or straight. The member has a distal piercing point and a proximal end for mounting or receiving a suture. Surgical needles are typically classified as either taper-point needles, wherein the diameter of the shaft tapers to a piercing pint, or cutting edge needles wherein the needles have various cutting edges along with piercing points to assist in penetrating various types of tissue.
Surgical sutures may be attached or mounted to the proximal ends of surgical needles in various ways. One common way is to have a channel formed into the proximal end of the needle. The channel end typically is die-formed into a needle during the manufacturing process and consists of a cavity. When a surgical suture end or tip is placed into the cavity, the channel end is hit with a die one or more times under pressure forcing the sidewalls closed tightly about the suture tip to prevent the suture from separating from the needle. The process of mounting a suture tip to the proximal end of a needle is known in the art as swaging. Another manner in which a suture may be mounted to a surgical needle is by drilling a hole, commonly referred to in the art as blind hole, into the proximal end of the needles. This can be done using conventional mechanical drilling apparatuses or conventional laser drilling apparatuses. The end or tip of a suture is then inserted into the drilled hole and the section of the proximal end of the needle surrounding the blind hole is swaged in a conventional manner by compressing with various conventional dies. It is also known to mount suture to surgical needles using conventional adhesives.
Surgical needles are conventionally manufactured from surgical grade alloys, such as surgical grade stainless steel, which are purchases from manufacturers in the form of rod or wire. The rod is drawn into wire and rolled onto a spool. The initial step in the manufacture of surgical needles is to remove the wire from the spool, degrease or clean if required, and then cut the wire into sections known as needle blanks. Each blank will have a length greater than the length of the finished needle, since material will necessarily be removed from the blank during the needle manufacturing process.
A conventional process for manufacturing a taper point needle typically consists of cutting wire into needle blanks and taking each needle blank and subjecting the blank to a series of grinding operations. This is conventionally done in the following manner. The needles blanks are fed into a conventional belt/stone grinding machine where they are given a distal tip. The needles are then transported individually or in bulk to a conventional needle drilling station wherein the needles are drilled using conventional carbide or tool steel drill bits to provide a proximal suture mounting cavity. The needles are then typically degreased and moved in bulk to a conventional belt/stone grinding machine for the finish taper grind and then to a curving machine to produce a conventional curved configuration. The needles are then cleaned, heat treated and may be electrochemically treated to additionally finish the needles. The conventional process is a batch process requiring the handling of the needles in bulk containers to transport them to and from the various work stations. Needles may become damaged or intermingled during such bulk transfers. In addition, the needles must typically be individually mounted in chucks in each machine at each work station. Although this chuck mounting step may in some circumstances be automated, it is typically a time consuming, labor intensive operation.
One conventional method of manufacturing cutting edge needles consists of initially cutting wire into blanks as described above. The distal tips of the needle blanks are then rotary swaged in a rotary swaging machine to produce a conical point having a spud. The spud is next partially cut and the needle blanks are then moved to a belt/stone grinder and mounted into chucks wherein the distal tip of each needle blank is given the final grind to create the necessary shape for bayonet closed die forming. The needle blanks are then moved in bulk or by chuck to a die station where each needle blank is die-formed. The needle blanks are then subjected to a series of grinding operations in a conventional belt/stone grinding machine to produce the cutting edge shape, for example, eight or more separate grinds. The needle blanks must be removed from the chucks and remounted in chucks after and prior to each grinding step, typically by using a walking beam mechanism. The extensive bulk and manual handling required by this process may result in damage to the needles, including the dulling of the points. In addition, the needle machines used in the prior art processes are operator dependent. Each operator tends to set up a machine differently resulting in variability in needle geometry and performance characteristics. Since surgical needles are quality control tested prior to release, the problems associated with the prior art processes tend to result in a financial burden upon the manufacturer in that a significant amount of the needles produced may have to be rejected and destroyed.
The previously described processes are labor intensive and typically utilize low speed, low output equipment. The needles are typically manually handled and transferred in bulk containers between various work stations or machines. In addition, numerous grinding steps are usually required. Often, needles are damages, including the dulling of needle points, due to the extensive handling and numerous grinding steps which are present in these processes. It is known that grinding operations are by their very nature imprecise resulting in wide variations in the dimensions of the finished needles. This imprecision resultingly yields a significant degree of geometric variability.
The disadvantages of the previously-mentioned prior art processes has been overcome in part by a process in which needle blanks are mounted to a carrier strip and moved to a plurality of finishing steps. Such a process is disclosed in U.S. Pat. No. 5,477,604 which is incorporated by reference. In this type of process, a taper point surgical needle is manufactured by progressively forming a needle blank. The tooling and dies referred to in this patent have been used and known in the art. It is commonly known to those skilled in the art of high speed forming and stamping that such tools and dies are not used alone. These tools are typically contained in holders or modules. These die set modules can then be placed in conventional larger more robust holders commonly referred to as a die post or die set. These larger systems are then placed and fastened into a die press. The presses can be free standing or contained as one or many presses (5 ton, 10 ton, 50 ton, etc.). The reasons for doing this are many, and vary throughout different industries. For example, with surgical needles accuracy, placement and repeatability are amongst the top. A system such as described above also allows for quick tool changes and reduced setup times, which increase machine efficiencies. A combination of these die sets can be arranged to produce the desired surgical needle or part. Typical die sets can contain a few or hundreds of individual parts that are integral to each other, e.g., die stops are commonly used to regulate or control the motion of a press. Tools or dies can be sensed using conventional devices such as conventional load cells to indicate tool wear. Tooling, dies and presses as described herein can be commercially purchased, or seen at trade shows in a variety of uses. The process consists of the initial step of cutting needle blanks from a roll of wire and mounting the blanks in a carrier. The carrier is cut and formed from strip located near the machine. The carrier transports the blanks to a succession of work stations on two different machines. At the initial machine and work station, the needle blank is coined in at least one conventional closed die having a cavity. Each needle blank is then moved successively to a trim station where flash is trimmed from the needle blanks using a punch and die. Optionally, the needle blank can be transported to one or more additional coining and trimming stations. Then each needle blank is moved to a grinding station wherein the needle blank is rotated about its longitudinal axis in the carrier as the distal tip of the needle blank is ground with a high speed grinding wheel parallel to the longitudinal axis of the needle blank. Needles are flattened and spooled prior to being moved to a second machine. This happens after the second machine which locates, curves and drills the blank. Following the coining and trimming operations described above, the needle points are ground to the final desired shape on contoured grinding wheels. Prior art grinding wheels are comprised of two plated profiled grinding wheels. This arrangement could result in needle chatter which may cause premature failure of the wheel that rotates in the same direction as the needle blank.
An improved configuration has been developed. Grinding wheels have been prepared consisting of a single plated profiled grinding wheel in concert with a non-plated hardened wheel. The plated wheel is plated with an abrasive such as Borzon or diamond. The non-plated hardened wheel can be preferably contoured or angled. Hardening of this wheel is necessary to reduce galling, scratching and pick-up on the non-plated surface. It was unexpected that such an arrangement would reduce needle chatter but it has proven to successfully reduce costs, improve point quality and reduce set-up times.
The grinding systems described in the prior art may exhibit build-up of grinding debris on the contoured surfaces of the wheels and within the workings of the machine. This results in shortened grinding wheel life and inconsistent grinding and bent needle blanks. It is commonly known that chemical bonding is often encountered when high speed grinding stainless steel with Borzon or diamond grit wheels. To eliminate this problem, a custom drip oiler cleaning system and method has been developed. This vacuum oiler system and method consists of dripping oil on the top portion of the grinding wheels with the drip aligned along the central longitudinal axis of the wheels and just proximal to the location of contact of the needle blank with the contoured wheels and a vacuum system located just distal to the location of contact of the needle blank with the contoured wheels (see. FIG. 22). The preferred location of the vacuum source is as shown in FIG. 22. Other locations for the vacuum source have been found to be less efficient in maintaining the grinding wheel surfaces in a clean state. The entire system is enclosed within a housing to contain all fluids and debris.
The primary function of the vacuum oiler cleaning system is not lubrication. It is unlike lubricating systems, which are used for cooling in wet grinding systems in that conventional lubricating systems simply employ conventional lubricants under constant flow and without vacuum recovery.
This combination of plated wheels, grit size, oil drip, vacuum, and transverse grinding on center of the hub allows for accurate high speed formation of each needle blank over millions of parts. High speed grinding as describe for this system can optimally range between 25 ms-150 ms of actual grinding time to complete the tapered point. Typical wheel life in this system ranges between 750,000 and 3.5 million needles.
After needles are fully processed on the first machine they are spooled and prepared for loading on the second machine for the drilling operation. The nature of the drilling operation is unique and requires a combination of a small incremental de-spooling of carrier strip with a greater incremental in-feed to the drilling. This requires the system to have the standard strip "push" and a strip "pull". The strip is pushed or fed from the spool and looped in an arrangement to allow lengths of the strip to accumulate. The drilling machine intermittently "pulls" required lengths of the strip for drilling operations. In this embodiment, de-spooling increments are about 0.5" and the intermittent length of strip pulled is about 2". This is a function of the number of drills in the drilling bank and will vary accordingly. Typically, there are at least two drills in the drilling bank. The drill heads, in each drilling bank, are separated from each other by 4". The needle blank is then cleaned, heat treated, and electrochemically treated. The finished needle is optionally siliconized.
In a variation of this process, the surgical needles are mechanically drilled to form distal suture mounting holes while the needles are mounted to the carrier strip. After the points are formed, the strip and needles are transported to a second machine where the blank is repositioned, curved using one or more stations or moved to a banked drilling station. Prior to the drilling station, the carrier is modified by cutting out a section to allow drilling. Needle making requires many operations occurring at a series of manufacturing stations. Needles may be held and moved between stations by use of a carrier strip. Manufacturing operations are required at both the proximal and distal ends of the needle blanks. Prior art carrier strips only allow for such operations to occur at one end of needle blanks. This necessitates the needles be singulated and possibly reloaded onto a second carrier strip for subsequent processing. A special carrier strip has been developed which allows for needle operations to occur at both the proximal and distal ends of needle blanks. This multipurpose carrier strip reduces cost and maintains constant control of the needle blank. This strip further includes access ports for removing a proximal portion of the needle tail upon completion of processing of the distal end of the needle blank. Once the proximal portion of the needle tail is removed, the needle blank is then repositioned and the back of the strip is trimmed away converting the strip so that subsequent needle hold drilling may be conducted on the proximal end of the needle.
The carrier strip includes two different tab designs. The first tab design is similar to those previously disclosed. The second tab design is unique in that it surrounds the distal portion of the needle tail and is subsequently formed around the distal portion of the needle tail and snapped back into the slot from which it was originally punched. This securely holds the needle in place. The second tab design is first pre-punched with very small holes at the stress points and subsequently cut to eliminate unwanted deformation of the strip. Any repetitive deformation of the strip will cause the strip to bow or camber. For example, a 0.0001" deformation associated with each second tab formation will result in a camber of 0.5" or greater over 5 to 6 feet. Deformation of this nature is unwanted in that it will result in needle twisting and jamming in subsequent operations. Where deformations of this nature are not preventable, off-setting deformations may be purposely made at other periodic locations along the carrier strip.
The multipurpose carrier strip of this process is used to process needles on two machines. The first machine fabricates the distal end of the needle and the second machine forms a drilled hole in a proximal end of the needle. Utilizing two machines, as described in this prior art process, both needle making and drilling operations are optimized. Needle making operations include point and body formation (including needle curving). Spooled needles formed following the first machine are later fed off the spool into a second machine in the opposite direction. That is to say, the last needle processed on the first machine is the first needle to be processed on the second machine. When feeding needles from the multipurpose carrier strip into the drilling machine, it is preferred that curved needle points trail the direction of feed off the spool. This minimizes point damage as the strip is pulled through the drilling machine. It is possible to combine both proximal and distal needle operations into one machine. However, if combined together into one machine, set-up times, efficiencies, set-up east and operator visibility are expected to be compromised.
A welding system may be utilized along with a custom alignment device to accurately attach the end of one strip to the beginning of a new strip. It is important that the strip pilot progression, or registration not be altered more than about +/-0.0002" to assure proper positioning in high speed manufacturing equipment. Other methods of connecting the strips together are possible such as clips, or tape, etc.
The drilling stations in such a drilling process consist of a bank of four or more conventional mechanical drills having conventional helical cutting edges. The drilling operation utilizes a unique progressive linear (4 up) arrangement which differs from conventional bank drilling systems. Conventional bank drilling systems utilize a rotary table having a series of stations which progressively drill deeper and/or larger holes in parts held in chucks which are spaced in increments less than the diameter of individual drilling heads. With this invention, the spacing of needles on the strip is 0.5". To overcome this problem, we have developed a unique linear single depth drilling system. The layout of drilling heads, the strip progression and needle registration are all considered. The strip is advanced in an intermittent fashion, allowing for drilling four non-consecutive needles on the strip. The system uses two drilling banks of four drilling heads each and has the ability of additional backup drilling banks if desired. Each drilling bank is driven by two servo motors and four drill motors. Backup drilling banks allow for the machine to continue to run if there is a failure with any of the primary drilling banks. Automatic switch over to the backup drilling banks can occur allowing an operator to correct any undesirable situation with the primary drilling banks. Alternately, individual drill heads have been equipped with quick disconnect collets to facilitate drill changes within seconds. The use of these collets eliminated the need for an automated switching to back up drilling banks due to undesirable situations occurring with any of the primary drilling banks. The drills may be modified to have an offset (see FIG. 20) point providing for a drilled hole which is larger than the outside diameter of the drill. Initially, the needles are moved to a bank of drills which provide a centering hole in addition a micropunch can be used to further aid in centering of the micro drills, then moved to a second set of drills which drill the suture mounting hole to the desired depth. It is commonly known by those skilled in the art of hole drilling to use a starter hole to keep small drills from "walking" around when they start to drill. In the manufacture of surgical needles, a center drilled hole is used and a separate hole drill is used to drill a blind hole. The depth of blind holes in surgical needles are typically 4-6 times the diameter of the drill used. A primary purpose of the center drill with surgical needle manufacturing is to assist in feeding suture machine into the hole in preparation for subsequent needle/suture attachment operations. Additionally, these center drilled holes provide a smooth burr free surface necessary to prevent damage to the later attached suture material. Center drilling can take the form of center drill or the like. A center drill has a conical shape and a flat point. The hole produced by such a center drill leaves a conical shape with a flat bottom. The size of the center drill required to produce a contour for suture insertion and attachment is large. While this size center drilled hole may be adequate for many subsequent drilling operations (to prevent small drills from "walking"), it is inadequate when the subsequent operation calls for a drill, such as a micro drill, with a diameter less than the width of the flat bottom section in the center drilled hole. This is often the case with surgical needles where the subsequent small drill to be used is very small. Thus, the function of the center drill is defeated and the small drill "walks" around on the flat bottom of the center drilled hole. To overcome this problem we developed a system to centrally punch the bottom of the center drilled hole. This improvement allows the micro drill to start in the center until the hole is deep enough that the side of the drill contact the walls of the center drill cone. This is particularly beneficial on drills smaller than 0.015" in diameter. The drilled needles are then moved to an optional plug depth measuring station to detect improperly drilled holes.
A special oil separator and recycling system has been used in conjunction with a vacuum system to evacuate the drill chip and excess lubricant from the hole and tooling area. This is an extremely critical step to the described process. Prior art has described the use of oil and/or air in an attempt to remove drill chips and lubricant from the drill. The conventional method was improved by cycling the spray of oil so that it is on only when required for drilling. Running the system in this manner maximizes the amount of oil on the drill during drilling and minimized the amount of oil consumption.
When using the previously-mentioned drilling process with a conventional progressive forming process, the needles are preferably spooled prior to drilling or fed directly to the drilling apparatus. If spooled, the spooled needles are loaded into a de-coiling apparatus which feeds the carrier and needles by means of conventional mechanical grippers to the second machine which repositions curves and drills. Carrier strips may be spooled on cores for transport between machines. Core diameter should be large enough so curved needles are not damaged by subsequent wraps of needles, and so that the needles are not loosened up by bending the strip over a small radius. Small needle wire sizes typically use a core of about 9 inches in diameter and achieve a spool size of about 2.5 feet or greater. Large diameter needles may reach 4 feet in diameter on the same size core. The curving and drilling apparatus could have various functions to turn and orient the needles for the various operations. The needles and carrier are then moved to a conventional curving station or multiple stations (four or more) where the needles are curved while still mounted to the carrier. The needles have an extra 1/2" to allow the complete curving of the blank. In later steps this extra portion will be repositioned and cut off. Next, the blank is repositioned, the strip and tails of the needles are cut using the pre-punched holes in the carrier. The strip is pushed into the loop and pulled into the drilling machine, the drills used for drilling are modified. The drill tips are altered to lengthen one side creating an off set center point. This offsets the center of the drill and allows the drill to cut a slightly larger, yet accurate hole. This technique increased drill life from about 1,000 needles per drill to over 15,000 needles per drill (there have been some drills that have lasted in the 30K to 75K range before breaking). Prior to this discovery, such drill life numbers using conventional drill types were not thought possible in high speed deep hole drilling of stainless steel material, especially where hole depths range between 4 and 6 times drill diameter.
The needle blanks (either straight or curved) are rotatably mounted on the carrier strip. This allows for axial and rotational motion. A section of the carrier is cut off to allow drilling, and the needles and carrier are then moved into a loop take-up prior to entering the first drilling station, where a bank of four conventional mechanical drills is used to drill the proximal end of each of the four needles which are not adjacent to each other. Accurate carrier and positioning systems (+/-0.0001 or 0.0002 tenths) allow for good locationing of work pieces in automated equipment. One means for achieving this accuracy comes from progressive on-line stamping of a carrier strip. Once formed, the carrier strip can be piloted throughout the process, this allows the equipment to have a sufficient clearance to minimize jamming of the carrier strip while maintaining accurate placement at the tool. Prior to drilling, the needles may be positioned to assure maximal alignment. It is preferred that the needles be counter sunk prior to the initial drilling step. The suture mounting hole may be drilled in a succession of depths by successive banks of drills at successive drilling stations. In addition, a conventional plug type probe may be utilized at a test station to test the depth of each drill. Improperly drilled needles are identified and not removed. The good needles are then removed from the carrier and the carrier is typically cut into sections for scrap disposal. It is possible to leave the needle on a strip as a spool or to cut into individual strip segments for further processing (in which case one would remove the bad needles)
There is a continuing need in this art for improved progressive forming processes for manufacturing taper point needles.